A) Field of the Invention
The present invention relates to a semiconductor device and its manufacture, and more particularly to a semiconductor device having a conductive layer made of a platinum group or alloy of a platinum group formed on a semiconductor substrate, and its manufacture.
B) Description of the Related Art
As the capacitance of a capacitor of a memory-based semiconductor device such as dynamic random access memories (DRAM) and ferroelectric memories (FRAM) becomes very large, the structure of the device is changing from a Metal-Insulator-Semiconductor (MIS) structure to a Metal-Insulator-Metal (MIM) structure. Materials of a ferroelectric film have been studied, including high dielectric materials such as tantalum oxide and strontium barium titanate and ferroelectric materials such as PZT and SBT. As the storage electrode of a capacitor, metal and conductive oxide excellent for its oxidation resistance is used. For example, such materials may be metal excellent for its oxidation resistance such as Ru, Ir and Pt, conductive oxide such as RuO2 and IrO2, conductive material having a perovskite structure such as SrRuO, as disclosed in Japanese Patent Laid-open Publications Nos. HEI-7-297364, HEI-8-335679 and HEI-8-340091.
An electrode made of these materials is formed by a physical film forming method such as sputtering and vapor deposition and thereafter by performing a heat treatment to improve tight contactness, reduce hillocks and pinholes and make the surface rough and the like.
Such metal of a platinum group has poor contactness with an insulating film. In order to enhance the tight contactness of a conductive film made of metal of a platinum group with an insulating film, a tight contact layer is disposed between the two films.
If a tight contact layer made of TiN, WN or the like is interposed when the inner surface of a contact hole having a high aspect ratio is covered with a conductive film made of metal of a platinum group or the like, coverage and morphology are degraded.